Calculation of an ablation plan

ABSTRACT

Systems and methods are described for planning of catheter ablation procedures, and in particular for planning of the placement of lesions and/or parameters used in ablation. In some embodiments, planning is based on thermal and/or dielectric simulation of lesions, individualized to the anatomy of the particular patient. Optionally, a plan comprises planning of a path along which an ablation lesion is to be formed, the ablation lesion optionally comprising one or more sub-lesions. The plan is optionally optimized for one or more criteria including, for example: minimization of path length, minimization of sub-lesion number, simplification of catheter maneuvering, avoidance of collateral damage to non-target tissue, access to the target dependent on anatomy shape and/or catheter mechanics, and/or features of the target anatomy such as tissue wall thickness and/or fiber direction.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/570,341, filed on Oct. 29, 2017, which is a National Phase of PCTPatent Application No. PCT/M2016/052688 having International Filing Dateof May 11, 2016, which claims the benefit of priority under 35 USC §119(e) of U.S. Provisional Patent Application Nos. 62/160,080 filed onMay 12, 2015; 62/291,065 on filed Feb. 4, 2016; and 62/304,455 filed onMar. 7, 2016. The contents of the above applications are allincorporated by reference as if fully set forth herein in theirentirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to systemsand methods for treatment with intrabody catheters and, moreparticularly, but not exclusively, to systems and methods for planningand/or dynamically adjusting planning of treatments such as ablationtreatments performed using intrabody catheters.

Catheterized intra-body ablation probes (for example, RF ablationprobes) are in use for minimally invasive ablation procedures. Suchprocedures are performed, for example, in the treatment of cardiacarrhythmia. In the control of cardiac arrhythmia, a goal of ablation isto create lesions in a pattern which will break pathways of abnormalelectrophysiological conduction which contribute to heart dysfunction(such as atrial fibrillation).

Single procedure success rates of catheter ablation at one year appearvariable. For example, they have been reported at 15%-60% (Sohns et al.,Catheter Contact Force: A Review of Emerging Techniques and Technologiesin AF Ablation. Journal Innov Cardiac Rhythm Management, 20145:1773-1780).

Earlier time post-procedure success percentages are generally higher.Gaps in the ablation line have been reported to contribute torestoration of impulse conduction (Ouyang et al., Recovered pulmonaryvein conduction as a dominant factor for recurrent atrialtachyarrhythmias after complete circular isolation of the pulmonaryveins: lessons from double Lasso technique. Circulation. 2005; 111:127-135).

One form of catheter ablation known as RF ablation relies on heatingcaused by the interaction between a high-frequency alternating current(e.g., 350-500 kHz) introduced to a treatment region, and dielectricproperties of material (e.g., tissue) in the treatment region. Onevariable affecting the heating is the frequency-dependent relativepermittivity κ of the tissue being treated. The (unitless) relativepermittivity of a material (herein, κ or dielectric constant) is ameasure of how the material acts to reduce an electrical field imposedacross it (storing and/or dissipating its energy). Relative permittivityis commonly expressed as where

${\kappa = {{ɛ_{r}(\omega)} = \frac{ɛ(\omega)}{ɛ_{0}}}},$

where ω=2πf, and f is the frequency (of an imposed voltage signal). Ingeneral, ε_(r) (ω) is complex valued; that is: ε_(r)(ω)=ε′_(r)(ω)+iε″_(r)(ω).

The real part ε′_(r)(ω) is a measure of how energy of an appliedelectrical field is stored in the material (at a given electrical fieldfrequency), while the imaginary part ε″_(r)(ω) is a measure of energydissipated. It is this dissipated energy that is converted, for example,into heat for ablation. Loss in turn is optionally expressed as a sum ofdielectric loss ε″_(rd) and conductivity σ as

${ɛ_{r}^{''}(\omega)} = {ɛ_{rd}^{''} + {\frac{\sigma}{\omega \cdot ɛ_{0}}.}}$

Any one of the above parameters: namely κ, ε, ε′_(r), ε″_(r), σ, and/orε″_(rd), may be referred to herein as a dielectric parameter. The termdielectric parameter encompasses also parameters that are directlyderivable from the above-mentioned parameters, for example, losstangent, expressed as tan

${\sigma = \frac{ɛ_{r}^{''}}{ɛ_{r}^{\prime}}},$

complex refractive index, expressed as n=√{square root over (ε_(r))},and impedance, expressed as

${Z(\omega)} = \sqrt{\frac{i\omega}{\sigma + {i\omega ɛ_{r}}}}$

(with i=√{square root over (−1)}).

Herein, a value of a dielectric parameter of a material may be referredto as a dielectric property of the material. For example, having arelative permittivity of about 100000 is a dielectric property of a0.01M KCl solution in water at a frequency of 1 kHz, at about roomtemperature (20°, for example; it should be noted that some dielectricproperties exhibit temperature dependence). Optionally, a dielectricproperty more specifically comprises a measured value of a dielectricparameter. Measured values of dielectric parameters are optionallyprovided relative to the characteristics (bias and/or jitter, forexample) of a particular measurement circuit or system. Values providedby measurements should be understood to comprise dielectric properties,even if influenced by one or more sources of experimental error. Theformulation “value of a dielectric parameter” is optionally used, forexample, when a dielectric parameter is not necessarily associated witha definite material (e.g., it is a parameter that takes on a valuewithin a data structure).

Dielectric properties as a function of frequency have been compiled formany tissues, for example, C. Gabriel and S. Gabriel: Compilation of theDielectric Properties of Body Tissues at RF and Microwave Frequencies(web pages presently maintained at//niremf(dot)ifac(dot)cnr(dot)it/docs/DIELECTRIC/home(dot)html).

SUMMARY OF THE INVENTION

There is provided, in accordance with some exemplary embodiments, amethod for planning an ablation plan of a target tissue in a patient,the method comprising: receiving data characterizing patient-specificanatomy comprising at least the target tissue, wherein the data includedata on dielectric properties associated with the target tissue;calculating by computer simulated results of one or more operations tolesion the target tissue, based on the received data; producing aplanned target form of the lesion, wherein the planned target form isselected based on one or more criteria evaluated on the simulatedresults; and providing an indication of the planned target form.

According to some embodiments, the data include data on thermalproperties associated with the target tissue.

According to some embodiments, the method comprises producing anablation plan for producing the planned target form.

According to some embodiments, the received data characterize geometryof the target anatomical structure, and the ablation plan describes theadjustment of parameters of ablation as a function of geometry along theplanned target form of the lesion.

According to some embodiments, the parameters of ablation are adjustedas a function of structure thickness along the planned target form ofthe lesion.

According to some embodiments, the received data characterize astructural anisotropy as a function of position in the target anatomicalstructure, and the ablation plan is produced based on consideration ofthe structural anisotropy.

According to some embodiments, the anisotropy comprises an orientationof myocardial fibers in the target anatomical structure.

According to some embodiments, the received data characterize thepositions of at least one existing lesion in the target anatomicalstructure, and the planned target form is adjusted to incorporate the atleast one existing lesion.

According to some embodiments, the target anatomical structure comprisesa cardiac wall.

According to some embodiments, the cardiac wall is a wall of an atrialheart chamber, and the planned target form of the lesion is selected forthe blockage of cardiac muscle contractile impulses contributing toatrial fibrillation, based on the computer simulated results of one ormore operations to lesion the target tissue.

According to some embodiments, the simulated results comprise thermalsimulation of the effect of lesioning on the patient-specific anatomy,based on thermal characteristics associated with the patient-specificanatomy.

According to some embodiments, the planned target form of the lesion isselected for transmural ablation of the target tissue, while avoidingcollateral damage to tissue in thermal contact with the target tissue.

According to some embodiments, the simulated results comprise dielectricsimulation of the effect of lesioning on the patient-specific anatomy,based on dielectric properties associated with the patient-specificanatomy.

According to some embodiments, the patient-specific anatomy furthercomprises non-target anatomical structure adjacent to the targetanatomical structure.

According to some embodiments, the calculating comprises simulation oflesion effects on one or more non-target anatomical structures, and theplanned target form is adjusted to avoid lesioning of the non-targetanatomical structure.

According to some embodiments, the non-target anatomical structurecomprises at least one from the group consisting of: a portion of anesophagus, a portion of a phrenic nerve, and portion of a vascular root.

According to some embodiments, the calculating produces simulatedresults simulating positions of a catheter used to perform the catheterablation; and wherein the planned target form is produced based onregions of the target anatomical structure which are accessible by thesimulated positions.

According to some embodiments, the simulated positions are constrainedby the mechanical properties of the catheter.

According to some embodiments, the simulated positions are constrainedby an anchor position applied to a portion of the catheter.

According to some embodiments, the received data comprises 3-D imagingdata of the patient-specific anatomy.

There is provided, in accordance with some exemplary embodiments, asystem for planning an ablation plan of a target tissue in a patient,the system comprising a processor configured to: calculate simulatedresults of one or more operations to lesion the target tissue, based ondata characterizing patient-specific anatomy comprising at least thetarget tissue; and produce an ablation plan comprising a set ofablations applied along an extent of the target tissue; wherein the datainclude data on dielectric properties associated with the target tissue;and wherein the ablation plan is produced based on based on one or morecriteria evaluated on the simulated results.

According to some embodiments, the data include data on thermalproperties associated with the target tissue.

According to some embodiments, the data characterize geometry of thetarget anatomical structure, and the ablation plan describes theadjustment of parameters of the ablations as a function of geometryalong the planned target form of the lesion.

According to some embodiments, the simulated results comprise thermalsimulation of the effect of lesioning on the patient-specific anatomy,based on thermal characteristics associated with the patient-specificanatomy.

According to some embodiments, the simulated results comprise simulationof lesion effects on one or more non-target anatomical structures, andthe extent of the set of ablations is adjusted to avoid lesioning of thenon-target anatomical structure.

According to some embodiments, the simulated results comprise simulationof lesion effects on one or more non-target anatomical structures, andablation parameters along the set of ablations are adjusted to avoidlesioning of the non-target anatomical structure.

There is provided, in accordance with some exemplary embodiments, amethod for dynamic adjustment of a plan for catheter ablation ofanatomical structure in a patient, the method comprising: receiving anablation plan for producing a target lesion, the ablation plandescribing a plurality of planned ablations by an ablation catheter to atarget anatomical structure; comparing at least one planned ablationfrom the plurality of planned ablations to tracking data describingongoing use of the ablation catheter; and adjusting the ablation plan,based on differences between the at least one planned ablation and thetracking data, wherein the adjusting comprises calculating simulatedresults of one or more operations to lesion the target anatomicalstructure, based on data characterizing patient-specific anatomycomprising at least the target anatomical structure.

According to some embodiments, the data characterizing patient-specificanatomy includes data on dielectric properties associated with thetarget anatomical structure.

According to some embodiments, the data characterizing patient-specificanatomy includes data on thermal properties associated with the targetanatomical structure.

According to some embodiments, the plurality of planned ablations isplanned as a sequence of ablation catheter activations corresponding toa sequence of position targets.

According to some embodiments, the ablation plan comprises a sequence ofablation parameter sets for activation of the ablation cathetercorresponding to the sequence of position targets, and wherein theadjusting comprises adjusting at least one of the ablation parametersets.

According to some embodiments, the adjusting comprises adjusting theablation parameters.

According to some embodiments, the differences comprise insufficientnearness of adjacency of lesioning in the tracking data, compared to theablation plan.

According to some embodiments, sufficient nearness of adjacencycomprises a gap between lesions produced at sequential positions whichare less than about 1.5 mm.

According to some embodiments, sufficient nearness of adjacencycomprises a gap between lesions produced at sequential positions whichare less than about 0.3 mm.

According to some embodiments, ablation plan comprises a relative timingof activations of the ablation catheter for lesioning while movingthrough the sequence of position targets.

According to some embodiments, the differences comprise a delay betweenablations, and wherein the adjusting comprises moving a position targetcloser to a previous position target, to prevent a gap in the lesion.

According to some embodiments, the differences comprise a delay betweenablations, and wherein the adjusting comprises increasing at least oneof the groups consisting of ablation duration and an ablation power, toprevent a gap in the lesion.

According to some embodiments, the method comprises calculatingsimulated results in the adjusted plan of one or more operations tolesion the target anatomical structure, and verifying that the simulatedresults avoid collateral damage to one or more non-target anatomicalstructures.

According to some embodiments, the simulated results comprise thermalsimulation of the effect of lesioning, based on thermal characteristicsassociated with tissue near the lesioning positions.

According to some embodiments, the simulated results comprise dielectricsimulation of the effect of lesioning, based on dielectric propertiesassociated with tissue near the lesioning positions.

There is provided, in accordance with some exemplary embodiments, asystem for dynamic adjustment of a plan for catheter ablation ofanatomical structure in a patient, the system comprising a processorconfigured to: receive an ablation plan for producing a target lesion,the ablation plan describing a plurality of planned ablations by anablation catheter to a target anatomical structure; compare at least oneplanned ablation from the ablation plan to tracking data describingongoing use of the ablation catheter; and calculate an adjustment to theablation plan, based on differences between the at least one plannedablation and the tracking data, wherein the adjusting comprisescalculating simulated results of one or more operations to lesion thetarget anatomical structure, based on data characterizingpatient-specific anatomy comprising at least the target anatomicalstructure.

According to some embodiments, the ablation plan comprises a sequence ofablation parameter sets for activation of the ablation cathetercorresponding to a sequence of position targets, and wherein theadjusting comprises adjusting at least one of the ablation parametersets.

According to some embodiments, the simulated results comprise thermalsimulation of the effect of ablation, based on thermal characteristicsassociated with tissue sites of the plurality of planned ablations.

According to some embodiments, the differences comprise insufficientnearness of adjacency of lesioning in the tracking data, compared to theablation plan; and wherein the adjusting is selected to prevent a gap inthe lesion, and comprises at least one of the group consisting of:moving a position target closer to a previous position target,increasing an ablation duration, and increasing an ablation power.

There is provided, in accordance with some exemplary embodiments, amethod for dynamic adjustment of a plan for catheter ablation ofanatomical structure in a patient, the method comprising: receiving anablation plan for producing a target lesion, the ablation plan includingsequence of position targets describing lesioning positions of a targetanatomical structure; comparing the sequence of position targets to asequence of tracked positions of an ablation catheter when the ablationcatheter is activated for forming a lesion; and adjusting the ablationplan, based on differences between the sequence of position targets andthe sequence of tracked positions, wherein adjusting comprisingcalculating simulated results of one or more operations to lesion thetarget anatomical structure, based on data characterizingpatient-specific anatomical structure comprising at least the targetanatomical structure.

There is provided, in accordance with some exemplary embodiments, amethod for planning an ablation plan of a target tissue in a patient,the method comprising: receiving data characterizing patient-specificanatomical structure comprising at least the target tissue; wherein thedata includes data on dielectric properties associated with the targettissue; calculating simulated results of one or more operations tolesion the target tissue, based on the received data; and producing aplanned target form of the lesion; and providing an indication of theplanned target form.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, some embodiments of the present invention may take the formof a computer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.Implementation of the method and/or system of some embodiments of theinvention can involve performing and/or completing selected tasksmanually, automatically, or a combination thereof. Moreover, accordingto actual instrumentation and equipment of some embodiments of themethod and/or system of the invention, several selected tasks could beimplemented by hardware, by software or by firmware and/or by acombination thereof, e.g., using an operating system.

For example, hardware for performing selected tasks according to someembodiments of the invention could be implemented as a chip or acircuit. As software, selected tasks according to some embodiments ofthe invention could be implemented as a plurality of softwareinstructions being executed by a computer using any suitable operatingsystem. In an exemplary embodiment of the invention, one or more tasksaccording to some exemplary embodiments of method and/or system asdescribed herein are performed by a data processor, such as a computingplatform for executing a plurality of instructions. Optionally, the dataprocessor includes a volatile memory for storing instructions and/ordata and/or a non-volatile storage, for example, a magnetic hard-diskand/or removable media, for storing instructions and/or data.Optionally, a network connection is provided as well. A display and/or auser input device such as a keyboard or mouse are optionally provided aswell.

Any combination of one or more computer readable medium(s) may beutilized for some embodiments of the invention. The computer readablemedium may be a computer readable signal medium or a computer readablestorage medium. A computer readable storage medium may be, for example,but not limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples (a non-exhaustivelist) of the computer readable storage medium would include thefollowing: an electrical connection having one or more wires, a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), an optical fiber, a portable compact disc read-onlymemory (CD-ROM), an optical storage device, a magnetic storage device,or any suitable combination of the foregoing. In the context of thisdocument, a computer readable storage medium may be any tangible mediumthat can contain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium and/or data usedthereby may be transmitted using any appropriate medium, including butnot limited to wireless, wireline, optical fiber cable, RF, etc., or anysuitable combination of the foregoing.

Computer program code for carrying out operations for some embodimentsof the present invention may be written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Java, Smalltalk, C++ or the like and conventionalprocedural programming languages, such as the “C” programming languageor similar programming languages. The program code may execute entirelyon the user's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Some embodiments of the present invention may be described below withreference to flowchart illustrations and/or block diagrams of methods,apparatus (systems) and computer program products according toembodiments of the invention. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example, and for purposes ofillustrative discussion of embodiments of the invention. In this regard,the description taken with the drawings makes apparent to those skilledin the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1A is a schematic flowchart of a method for planning of an ablationplan, in accordance with some exemplary embodiments of the presentdisclosure;

FIG. 1B is a more detailed schematic flowchart of a method for planningof an ablation plan, in accordance with some exemplary embodiments ofthe present disclosure;

FIG. 2A is a schematic illustration of a tissue wall of a left atrium,including roots of left and right pulmonary veins, and a preliminaryline of planned ablation, in accordance with some exemplary embodimentsof the present disclosure;

FIG. 2B is schematic illustration of tissue wall, together with asection of a phrenic nerve, an esophagus, and roots of pulmonary veins,each of which is potentially vulnerable to lesion damage due toproximity with tissue wall, in accordance with some exemplaryembodiments of the present disclosure;

FIG. 2C is a schematic illustration of a planned set of ablationsub-lesions for ablating along line of planned ablation, in accordancewith some exemplary embodiments of the present disclosure;

FIG. 2D is a schematic illustration of different positions along plannedablation line reached by respective different positionings of anablation catheter from a common septal insertion position, in accordancewith some exemplary embodiments of the present disclosure;

FIG. 2E is a schematic illustration of an alternative line of plannedablation, in accordance with some exemplary embodiments of the presentdisclosure;

FIGS. 3A-3B schematically illustrate aspects of the planned placement ofsub-lesions of a lesion line related to myocardial fiber direction, inaccordance with some exemplary embodiments of the present disclosure;

FIG. 3C is a schematic illustration highlighting details of a plannedset of sub-lesions of a lesion line, and their traversal along a line ofplanned ablation, in accordance with some exemplary embodiments of thepresent disclosure;

FIGS. 4A-4B schematically illustrate changes in planned lesion extent asa function of tissue thickness, in accordance with some exemplaryembodiments of the present disclosure;

FIGS. 5A-5B schematically illustrate planning for adjacency effects oftissue lesions made in two different sequences, in accordance with someexemplary embodiments of the present disclosure;

FIG. 6 schematically illustrates a method of real-time use of anablation plan with optional adjustment, in accordance with someexemplary embodiments of the present disclosure;

FIGS. 7A, 7B and 7C illustrate the 3-D display of a lesion plan for aleft atrium, in accordance with some exemplary embodiments of thepresent disclosure;

FIG. 8A illustrates the 3-D display of a planned lesion ablation linefor a left atrium, along with an ablation probe, in accordance with someexemplary embodiments of the present disclosure;

FIG. 8B illustrates an interior-D view of left atrium, probe, andplanned ablation line, in accordance with some exemplary embodiments ofthe present disclosure;

FIGS. 9A, 9B and 9C schematically illustrate aspects of lesioning toblock of tissue conduction, for example for the treatment of atrialfibrillation, in accordance with some exemplary embodiments of thedisclosure;

FIG. 10 is a schematic flowchart of a method for generating a tissuesimulation including thermal and dielectric properties, in accordancewith some embodiments of the present disclosure;

FIG. 11 is a block diagram of components of a system for tracking theposition of an intra-body catheter, which is also optionally configuredas a system for lesion planning, in accordance with some embodiments ofthe present disclosure;

FIG. 12 is a flowchart of an exemplary method for generating the thermalcomponent of the generated simulation, in accordance with someembodiments of the present disclosure;

FIG. 13A is a graph depicting the calculated PLD pattern created by anelectrode (e.g., RF ablation electrode(s)) in a tissue, in accordancewith some embodiments of the present disclosure;

FIG. 13B is a graph depicting the calculated temperature pattern (indegrees Celsius) created by an electrode (e.g., RF ablationelectrode(s)) in a tissue, in accordance with some embodiments of thepresent disclosure; and

FIG. 14 is a schematic representation of software modules and associateddata for use in ablation planning, according to some exemplaryembodiments of the present disclosure.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to systemsand methods for treatment with intrabody catheters and, moreparticularly, but not exclusively, to systems and methods for planningand/or dynamically adjusting planning of treatments such as ablationtreatments performed using intrabody catheters.

Overview

An aspect of some embodiments of the current invention relates tosystems and methods for planning catheter ablation of a tissue in apatient (producing what is referred to herein as an ablation plan).

In some embodiments, the method comprises receiving (for example,receiving by a lesion planning system, by a processor configured toimplement lesion planning, and/or from a user) of an indication of apreliminary target form of a lesion to be formed on and/or within atarget anatomical structure of the patient by the planned catheterablation. Optionally, the preliminary target form is indicated as a path(for example a continuous path, and/or a path described as a series oflocations to be lesioned) specified with respect to a representation(e.g., a 3-D display) of patient-specific anatomy.

In some embodiments, the method comprises calculating (e.g., by a lesionplanning system) simulated results of lesioning, based on thecharacterization of data describing patient-specific anatomy. Simulatedresults may include short-term effects such as heating, collateraleffects on nearby tissue, reversible block, and/or edema; as well aspredictions of long-term effects such as the irreversibility of block.In some embodiments, the simulation is based on thermal and/ordielectric tissue properties specified in the received data. In someembodiments, the simulation comprises simulation of the effects of powerloss density (PLD) in tissue under excitation by a RF field modeledafter a field produced by an RF ablation catheter. Optionally, whennon-RF ablation is performed (such as by substance injection,cryoablation and/or irreversible electroporation), another equation isused to simulate the initial distribution of ablating energy to (or itsablating removal from) tissue. Additionally or alternatively, simulationof thermal conduction is also performed (for example, based on thethermal continuity equation). Optionally, simulation comprisesaccounting for interaction between thermal and dielectric properties,for example, changes in dielectric properties during heating as a resultof temperature change potentially subsequently influence heating itselfin turn. Optionally, simulation comprises accounting for interactionbetween ablation and physiological responses, for example, edema arisingpost-ablation potentially affects how later attempts to ablate the sameand/or a nearby region proceeds. Optionally, this is accounted forbetween sequential sub-lesions, and/or as an ablation probe moves alonga line of planned ablation.

In some embodiments, the simulated results are used in planning a targetform of a lesion (e.g., in planning an ablation). Optionally, theplanning comprises planning a line of planned ablation (e.g., a line oflocations at which ablation is performed to create sub-lesions), alongwhich a lesion is to be formed. Optionally, the plan comprisesspecification of ablation parameters to be used along the line—forexample, particular positions, angles, and/or pressures for contactbetween an ablation probe and target tissue; energies used to activatethe probe (optionally including frequency and/or voltage); selection ofelectrodes (optionally including specification of phased activation ofelectrodes); and/or durations of ablation. Optionally parameters ofablation (for example, parameters defining energies, details ofpositioning, and/or durations) are varied at different positions alongthe line of planned ablation. Optionally, simulation is also used indetermining the order of ablations, for example, where ends of a loopingline of ablation should meet, and/or placement and/or timing ofsub-lesions to take advantage of previously existing lesions and/orrecent administration of ablation energy. Herein, the term “sub-lesion”is used to indicate portions of a larger lesion created by an ablationprobe upon or along a portion of larger area to be lesioned (e.g.,defined as a line or path, but not excluding definitions as areas orvolumes). A larger lesion is optionally created by a probe movedstepwise between lesion foci (with ablation at each step defining asub-lesion), and/or by dragging an ablation probe over a continuousextent of target tissue (where a sub-lesion is defined by the extent ofdragged-out ablation, and/or optionally by a change in parameter, forexample, a change in ablation power, rate of drag, or anotherparameter).

In some embodiments, the planning comprises automatic adjustment of thepreliminary target form of the lesion to satisfy one or more criteriaand/or constraints; for example, criteria and/or constraints affectingsafety, procedure outcome, efficiency of power application, and/ortreatment duration; and/or practicability of the lesion plan.Optionally, the lesion plan takes into account (and is formulated toavoid damaging) the patient-specific positions of anatomical structuressubject to collateral damage (for example, the esophagus, phrenic nerve,and/or venous roots, as in the case of ablations to treat atrialfibrillation). Optionally, the ablation plan takes into account aspectsrelated to maneuvering within the confines of an anatomical space. Forexample, there may be mechanical limitations on the maneuvering of anablation catheter. In another example, a requirement for precision ofplacement may be relaxed in some positions along a line of plannedablation (e.g., a tolerance to gaps in a lesion line may be greaterwhere fibers are oriented so that they are cut by, rather than runningbetween, adjacent sub-lesions); while certain maneuvers (such as joininglesion line ends) are potentially more prone to error and/orcomplication. In some embodiments, an ablation plan is designed to matchmore difficult maneuvers to lesion positions where delay and/or error ispotentially less damaging to the end result. In some embodiments, theablation plan is calculated for a shortest line of planned ablation, aminimal number of sub-lesions placed, and/or a minimal use of ablationenergy, compatible with the relative importance (e.g., priority and/orweighting) of other criteria and/or constraints.

In some embodiments, the method comprises providing (for example, to alesion planning system) of an indication of the planned target form.Optionally, the indication comprises showing a line of planned ablationtogether with a 3-D representation of the target anatomical structure.Optionally, the indication also comprises display of targeted ablationpositions along the line, and/or the order and/or timing in which theablation positions are to be targeted. The indication may also includedetailed aspects of the plan such as planned lesion size and/orlesioning parameters such as power and duration. In some embodiments, anablation plan includes the definition of intermediate target resultswhich can be monitored while the plan is carried out. For example,properties of a lesion may be monitored during an ablation in progress(for example, based on dielectric property and/or thermal measurements).In some embodiments, intermediate target results are used to adjust oneor more parameters of the ablation in progress, and/or another parameterof the ablation plan.

In some embodiments, a preliminary target form is provided automaticallyand/or by a user as an indication of a selection of a more generallyspecified lesion form, for example, a selection specified in terms ofone or more anatomical landmarks, and/or a topographic relationship ofthe lesion with respect to the landmarks. For example, the indicationmay be “surrounding a root of a pulmonary vein” (additionally oralternatively, the root of a plurality of veins, of another bloodvessel, or any other relationship between anatomical landmark and lesionform suitable to the application).

In some embodiments, the data characterizing patient-specific anatomycomprise 3-D imaging data (for example, MRI, CT, NMR, and/or data fromanother imaging modality) describing and/or displaying patient-specificanatomy. In some embodiments, the received data are marked (and/orcharacterized after receipt) with respect to thermal and/or dielectricproperties. Optionally, thermal properties include, for example, thermalconductivity, heat capacity, rate of active heat transfer (for example,by blood perfusion), and/or rate of metabolic heat generation.Optionally, dielectric properties include, for example, thefrequency-dependent relative permittivity of tissue, and/or anotherproperty related to relative permittivity; for example, as described inthe Background of the Invention, herein.

In some embodiments, an ablation plan includes specification of whereablation is to occur; optionally defined as a line or path, an area,and/or a volume (herein, ablation plans for a path are provided asexamples, without limitation away from embodiments using areal orvolumetric specifications). An ablation plan optionally comprises thedefinition of ablation parameters along the ablation line (for example,frequency, total energy delivered, power and/or timing). An ablationplan optionally specifies movements of an ablation probe moreparticularly—for example, from what start point, in what order, to whatend point, at what angle, and/or with what timing between movements.Optionally, the plan includes specification of the ablation catheteritself.

An aspect of some embodiments of the current invention relates tosystems and/or methods of dynamic adjustment of a plan for catheterablation of a tissue in a patient. In some embodiments, differencesbetween an ablation plan and the actual ablation as it occurs areautomatically adjusted for by changing the plan in media res, optionallywhile still taking into account criteria and/or constraints affectingsafety, procedure outcome, and/or speed and/or practicability of thelesion plan. Plan adjustments may occur entirely automatically, and/orbe provided as suggestions and/or alternatives for a user to followand/or select among. Optionally, alternatives (particularly when theyare presented in response in the contingency of a complication or errorin the procedure) are presented with an indication of likely relativerisks/benefits.

In some embodiments, an ablation plan (for example, an ablation plan asjust described) is received; for example, received by a systemconfigured to track an ablation catheter during ablation. In someembodiments, the ablation plan includes a sequence of position targetsdescribing lesioning positions of a target anatomical structure at whichsub-lesions and/or other portions of a completed larger lesion areplanned to be created. Optionally, the sequence comprises a discretesequence—for example, a sequence of spot-like sub-lesions along a lineof planned ablation. Optionally, the sequence comprises continuoussequence—for example, a sequence of positions passed through as anablation catheter is dragged along a portion of a line of plannedablation.

In some embodiments, the sequence of position targets is compared to theactual (e.g., tracked by a catheter tracking system) positions of anablation catheter where it performs ablation. Preferably, the comparisonoccurs during an ablation procedure. Optionally, this is followed byautomatic correction (optionally augmented by user input such asconfirmation and/or selection of options) before certain difficultiescaused by delay arise—for example, loss of lock between the relativeposition of the ablation catheter and the lesion, and/or evolution ofthe lesion to a form which may be more difficult to lesion (tissuetypically becomes edematous within a few minutes of lesioning, which canin turn make it difficult to reliably make further lesioning adjustmentsafterward).

In some embodiments, the ablation plan is adjusted, based on differencesbetween the sequence of position targets and the sequence of trackedpositions. Generally, the adjustment seeks to preserve key features ofthe final lesion which are potentially at risk due to a partialdeviation from the plan. One significant form of error which can arisein the treatment of atrial fibrillation by lesioning is the placement ofsub-lesions which are not sufficiently close to prevent impulsetransmission from crossing between them. In some embodiments, the planis adjusts by inserting one or more additional lesions, and/or by addingfurther lesioning energy at one of the sub-lesion positions. At the sametime, in some embodiments, safety constraints are also imposed on theplan: for example, to prevent collateral damage to sensitive structuressuch as the esophagus, venous roots, autonomic ganglia, and/or phrenicnerve.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings. The invention is capable of otherembodiments or of being practiced or carried out in various ways.

Method for Planning an Optimal Ablation Line

Reference is now made to FIG. 1A, which is a schematic flowchart of amethod for planning an ablation plan (e.g., defining an ablation linewhich is optimal according to some selected combination of criteriaand/or constraints), in accordance with some exemplary embodiments ofthe invention. In some embodiments, the planning comprises indicating bya user of a target lesion result (at block 151). Optionally oralternatively, the indication is provided at least partiallyautomatically. At block 152, in some embodiments, conditions andconstraints which affect how the lesion result is most preferablyachieved are characterized, optionally including the use of imaging datadefining tissue types and positions, data describing dielectric and/orthermal characteristics of tissue, and/or user input serving as guidancefor the choice of specific optimization method.

At block 153, in some embodiments, an ablation plan is defined, based onthe indicated target lesion result, the characterized conditions andconstraints (and optionally on a selected method and/or selectedparameters of how planning is to be performed based on the otherinputs).

Optionally, expected results of an ablation plan are presented to a usera priori, for example, as an ablation line indication presented togetherwith a 3-D model of the target tissue, as one or more estimates of timeof ablation (partial or overall), as a likelihood of successfultreatment, etc. In some embodiments, likelihood of successful treatmentis calculated based on success in other patients having similar ablationprocedure characteristics.

In some embodiments, an ablation plan includes specification of whereablation is to occur; optionally defined as a line or path, an area,and/or a volume (herein, ablation plans for a path are provided asexamples, without limitation away from embodiments using areal orvolumetric specifications). An ablation plan optionally comprises thedefinition of ablation parameters along the ablation line (for example,frequency, total energy delivered, power and/or timing). An ablationplan optionally specifies movements of an ablation probe moreparticularly—for example, from what start point, in what order, to whatend point, at what angle, and/or with what timing between movements.Optionally, plan includes specification of the ablation catheter itself.

In some embodiments, operations of blocks 152 and 153 in particular arecarried out by application of a thermal and/or dielectric propertysimulation of the tissue to be treated. Characteristics of thesimulation are described, for example, in relation to FIGS. 10-13Bherein.

Reference is now made to FIG. 1B, which is a more detailed schematicflowchart of a method for planning of an ablation plan, in accordancewith some exemplary embodiments of the invention. The operationsreferenced by the blocks of FIG. 1B are described in conjunction withinterleaved descriptions relating to other figures, for example, FIGS.9A-9C, 2A-2E, 3A-3C, 4A-4B, and 5A-5B.

Inputs for Planning an Ablation Plan Treatment by Tissue Lesioning

In some embodiments, ablation treatment of a tissue region such as atissue wall (for example, cardiac tissue of the atria) comprises theformation of a substantially continuous lesion of tissue which serves asa block to conduction. In some embodiments, the targeted region of blockis along a lesion path formed from a plurality of sub-lesions arrangedalong it a substantially contiguous fashion.

Effective blockage treatment of an irregular impulse conduction diseasesuch as atrial fibrillation potentially fails when the blockage isbroken or incomplete. However, the procedure for forming a blockinglesion is subject to conflicting requirements, such as the need to avoidcollateral damage to non-target tissue, the difficulty of maneuvering acatheter subject to constrained degrees of freedom, and time pressure tocomplete the procedure as quickly as possible.

Reference is now made to FIGS. 9A-9C, which schematically illustrateaspects of lesioning to block of tissue conduction, for example for thetreatment of atrial fibrillation, according to some exemplaryembodiments of the present disclosure. Shown in FIGS. 9A-9B is a lesionpath 54A which encircles two pulmonary veins 48 of a left atrium (a viewfrom inside the atrium is shown).

In some embodiments, an ablation probe 10 comprising at least oneablation device 103 is moved sequentially along path 54A, ablating at aplurality of locations to create a chain sub-lesions 52 at eachlocation. In some embodiments, ablation device 103 comprises anelectrode, e.g., an electrode used in RF ablation. Optionally, theelectrode acts as a sensing electrode for dielectric properties of thetissue near it. Optionally, an additional electrode is provided forsensing dielectric properties.

In FIG. 9B, impulse 955 is shown arising from the vicinity of apulmonary vein 48. Where it encounters a completed lesion 52 (forexample, at boundary 955A), conduction is stopped. However, a gap 52Bpotentially allows impulse portion 57 to escape into surrounding tissue,where it may contribute to an irregular heartbeat. The minimum size of agap allowing conduction can be, for example, about 1.0 mm, 1.3 mm, 1.5mm, or another larger, smaller or intermediate value.

Insofar as lesions may compromise a non-uniform profile through thethickness of a tissue (e.g., as for a hemi-ellipsoid or paraboloid), itshould be understood that any region throughout the tissue thicknessexceeding this gap width (as long as it has sufficient depth, forexample, 0.55 mm, or another value of at least about 0.5 mm-2 mm, tosupport transmission) can serve as a pathway for impulse “escape”. Thus,lesions which superficially contact one another, or even overlap—even iftransmural at some region—may nonetheless (at least in principle) besufficiently distant at some depth to allow impulse escape therebetween.However, for purposes of discussion and illustration, at least partiallytransmural lesions shown herein as superficially contacting aregenerally assumed to be close enough to block transmission therebetweenat any depth, except as otherwise indicated.

The maximum size of the gap which still prevents blockage may alsodepend on the structure of the underlying tissue; for example, adirection of myocardial fibers in relation the orientation of the gap(this is also discussed herein, for example, in relation to FIGS.3A-3B). Optionally, the relevant orientation (which potentially variesthrough the thickness of the tissue) is selected from one or more layersin which the gap may exist.

FIG. 9C illustrates how lesion depth potentially relates to relativelyeffective or ineffective conduction block. Tissue region 50 is shownwith a chain of lesions 52, 52A, 52D, 52C already formed. The variousdepths of these lesions are schematically outlined as dotted lineparaboloids 53.

Electrode 103 is shown in contact with a surface of tissue 50, overlesion and targeted tissue area 52C. Here, the lesion is transmural, tothe degree that it has begun to to spread across the opposite surface oftissue 50 at region 53C. Lesion 52A is also a deep lesion, but thedegree of transmurality is lower (for example, a small distance 53A hasbeen left). This may not be a reason for concern, if gap 53A is toosmall to allow impulse conduction. However, at lesion 52D, the lesion istoo shallow, and gap 53D is sufficiently large to allow impulse portion57 to pass through it. In some embodiments, a transmurality gap of about0.55 mm or smaller is considered small enough to prevent impulse escape,depending also in part on the width of the gap.

Although ablation is generally described herein with respect to ablationof an atrial wall for the treatment of atrial fibrillation, it should beunderstood that the descriptions also apply, changed as necessary, tothe planning of ablation in other tissues; for example: neural tissue,tumor tissue (for example, cancer), other abnormal growth tissue such aswarts, skin tissue, mucous membrane, or another tissue.

Preliminary Planning of an Ablation Line

Returning to FIG. 1B: The flowchart begins; and at block 110, in someembodiments, a preliminary line of planned ablation 54 (e.g., lesionpath 54A) is defined. The definition is optionally by a user drawing orotherwise indicating a line (for example, on a computerized display of aschematic and/or anatomical representation of the target region).Optionally, the user indicates a preferred preliminary line type (e.g.,by selecting from a menu a target such as “around the superior leftpulmonary vein root”, or another such target). Optionally, a preliminaryline of planned ablation 54 is automatically generated and/or selectedbased on the indication. Optionally, automatic calculation of a finalline of planned ablation proceeds directly from the basic indication ofan ablation target; for example, based on criteria described in relationto blocks 112, 114, 116.

The line of planned ablation can be defined on any suitable tissuesurface; for example, within the left atrium (e.g., around one or morepulmonary veins), or within the right atrium (e.g., around one or morebranches of the vena cava). For purposes of discussion, the example ofan ablation line in a left atrium is described, however it is to beunderstood that the discussion also applies, changed as necessary, tothe definition of ablation lines along other surfaces.

Reference is now made to FIG. 2A, which is a schematic illustration of atissue wall 50 of a left atrium, including roots of left and rightpulmonary veins 47, 48, and a preliminary line of planned ablation 54,in accordance with some exemplary embodiments of the invention.

Optionally, preliminary line of planned ablation 54 encircles both leftpulmonary veins, for example as shown. Optionally, for example asdiscussed with respect to the remainder of FIG. 1B, the line of plannedablation serves as a basis for further modifications which result in afinal ablation line which satisfies certain criteria of safety and/oreffectiveness. Optionally, as discussed in particular with respect toFIG. 2E, the line of planned ablation is also optimized to a minimallength and/or minimal number of ablation needed to isolate one or morefeatures such as vein roots which preliminary line of planned ablation54 surrounds, and/or otherwise delineates, indicates, and/or selects.

Returning to FIG. 1B: in some embodiments, based on the preliminary lineof planned ablation (or other target definition), further criteria areevaluated for use in the definition of an optimal path of ablation.Optionally, actions of one or more of blocks 112, 114, and 116 areperformed in sequence and/or in parallel. These blocks correspond tooperations taking place within block 152 of FIG. 1A.

Data for Optimizing an Ablation Line—Protective Constraints

At block 112, in some embodiments, protective constraints areestablished with respect to the line of planned ablation.

Reference is now made to FIG. 2B, which is schematic illustration oftissue wall 50, together with a section of a phrenic nerve 45, anesophagus 44, and roots of pulmonary veins 47, 48; potentiallyvulnerable to lesion-damage around preliminary line of ablation 54 dueto proximity with tissue wall 50 at regions 61, 62, 63, or 64; inaccordance with some exemplary embodiments of the invention.

In some embodiments, a planned ablation of one tissue (e.g., tissue wall50) involves potential risk of damage to one or more adjoining tissues.For example, thermal ablation (e.g., by RF energy application) whichenters into region 62 of tissue wall 50 potentially also induces heatingin esophagus 44 which could lead to damage. Region 61, adjacent to aportion of phrenic nerve 45, is another region of potential risk;damaging the phrenic nerve can lead to partial respiratory paralysis. Insome embodiments, lesion placement criteria exclude and/or limitlesioning from entering certain regions of the lesioned surface itself.Regions 63 and 64 are defined, for example, to exclude lesions fromentering the ostia of the pulmonary veins.

In some embodiments, thermal simulation of ablation (where ablation isby heating and/or cooling) is used to define adjacency which leads torisk of collateral tissue damage. Thermal simulation is described, forexample, in relation to FIGS. 10-13B herein. In some embodiments,simulation is of ablation by another method, for example,electroporation.

In some embodiments, the simulation results are processed to create adefinition of regions of tissue wall 50 which are preferably excludedfrom ablation, and/or preferably ablated only with parameters tuned toreduce a likelihood of collateral damage. Optionally, the regiondefinition is expressed as a region preferably excluded fromconsideration as central contact points for an ablation probe. Forsimplicity of illustration, the schematic representation of FIG. 2B maybe understood as adopting this type of definition.

Additionally or alternatively, exclusion is otherwise defined. Forexample, the definition may be such that no heating or cooling of anat-risk tissue can rise above (or fall below) a certain temperaturethreshold, according to a simulated ablation operation. In someembodiments, the temperature threshold is, for example, about 50° C.,55° C., 58° C., 60° C., 65° C., 70° C., 75° C., or another larger,smaller or intermediate temperature. Optionally, a functional criterionis used: for example, a plan which includes heating for more than Tseconds at energy Y by a probe within X mm is preferably excluded.Optionally, values for T, Y and/or X are chosen based on generalsimulations and/or experimental data, for use as heuristics in the casesof actual patient treatments. For example, T is varied between about 15seconds to about 45 seconds; Y varies between about 15 W and 30 W,and/or X varies between about 5 mm-10 mm. Use of heuristic criteria hasthe potential advantage of bypassing at least some of the computationalload of an individualized simulation.

Result-focused criteria potentially allows more flexibility in definingan ablation plan than a strict spatial exclusion criterion. For example,lesioning in a risky area is made potentially safer by controllingparameters such as ablation power and/or ablation timing, optionally inaddition to controlling the parameter of ablation probe placement.Conversely, there may be regions where the risk of collateral damage isrelatively low. For example, relatively low thermal conductivity ofadjacent tissue (e.g., air-filled lung tissue) potentially allows moreaggressive lesioning of heart wall tissue, which has a potentialadvantage for speed of lesioning.

Data for Optimizing an Ablation Line—Access Constraints and Conditions

Returning again to FIG. 1B: at block 114, in some embodiments,constraints and conditions relating to spatial access to a lesion lineare defined.

Reference is now made to FIG. 2D, which is a schematic illustration ofdifferent positions along planned ablation line 55 reached by respectivedifferent positionings 242, 241, 243 of an ablation probe 10 from acommon septal insertion position 245, in accordance with some exemplaryembodiments of the invention.

In some embodiments, this comprises using a 3-D anatomical modeltogether with a model of the mechanical control characteristics of anablation probe 10 to calculate which parts of the target region can bephysically reached for ablation. In some embodiments, the calculation isadditionally constrained, for example, by the location of one or moreanticipated access ports 245. For example, an anticipated location oftrans-septal penetration, and/or the position of a blood vessel used forcatheter access are assumed as part of the spatial access definition.

Optionally, the spatial access constraints and conditions includespecification of which target surface regions, e.g., of tissue wall 50can or cannot be reached (optionally, reached from a particular accessport 245). In some embodiments, conditions further indicate where accessis effectively continuous through some range of ablation probe 10movements. For example; in FIG. 2D, a potentially continuous sequence ofcontrol movements allows ablation along line of planned ablation 55between position 242 and position 243. However, control movements toallow lesioning in the other direction potentially encounter adiscontinuity, e.g., between positions 242 and 241. By “discontinuity”in this context, is meant a condition where an incremental change in thecontrol inputs to ablation probe 10 cannot be used to make acorresponding incremental change in a selected position of ablationalong an ablation path (e.g., because ablation probe 10 has reached alimit of movement). However, it may be possible to proceed along thepath by resetting the control degrees of freedom to anotherconfiguration, introducing thereby “discontinuity” in control movementsrelative to path position. Use of this information is described, forexample, in relation to the definition of a path traversal plan at block120.

Data for Optimizing an Ablation Line—Target Characteristics

At block 116 of FIG. 1B, in some embodiments, the ablation target itselfis characterized with respect to criteria affecting lesion pathplanning.

Reference is now made to FIGS. 4A-4B, which schematically illustratechanges in planned lesion extent 401A, 402B of lesions 401, 402, intissue walls 50A, 50B as a function of tissue thickness 51A, 51B, inaccordance with some exemplary embodiments of the invention.

In some embodiments, a goal of ablation is to create a blockage lesionhaving a substantially transmural extent. To meet this goal, thickertissue walls potentially require application of more lesioning energy(e.g., at a higher power and/or for a longer time) than thinner walls.Over-lesioning, however, can weaken the tissue, and/or lead to damage tosurrounding tissue. Over-lesioning can also extend lesioning timeunnecessarily. In some embodiments, tissue thickness throughout theregion targeted for lesioning is characterized, for example based onanalysis of anatomical images of the individual patient (obtained, e.g.,by MRI, CT, or another method), and/or based on tissue atlasinformation.

Reference is now made to FIGS. 3A-3B, which schematically illustrateaspects of the planned placement of lesions 301, 302, 303, 304 relatedto myocardial fiber direction, in accordance with some exemplaryembodiments of the invention.

In some embodiments, the maximum impulse-blocking distance 305, 307between two sub-lesions 301, 302, 303, 304 centered on points 301C,302C, 303C, and 304C, respectively, is predicted in part by theorientation of myocardial fibers 66, 67 in the region of the gap. Ingeneral, fibers running parallel to the direction of impulse flow acrossthe gap can transmit impulses through a smaller gap (for example, a gapof no more than about 0.3 mm, 0.4 mm, 0.5 mm, or another distance) thanfibers running perpendicular to it (where the maximum size of aninhibiting gap may be, for example, about 1 mm, 1.5 mm, 2 mm, or anotherdistance). Discussion of the influence of fiber orientation and gap sizeon myocardial fiber impulse transmission is found, for example, inRanjan et al. (Gaps in the Ablation Line as a Potential Cause ofRecovery From Electrical Isolation and Their Visualization Using MRI.Circ Arrythm Electrophysiol 2011; 4:279-286). In the computationalmodeling of Ranjan et al., the reported maximum gap at whichconductivity failed was 1.4 mm when fiber direction was perpendicular tothe ablation line. When fiber direction was parallel to the ablationline, conductivity failure was reported only up to 0.3 mm gaps. Ranjanet al. suggest that larger gaps which appear to at least initially blockconduction in in vivo studies may include tissue with temporarilyreduced conductivity which could later recover and resume conduction.

In some embodiments of the invention, myocardial fiber orientation ismodeled from anatomical atlas data giving typical orientations, and/ormeasured for the individual patient using, for example,echocardiography-based shear wave imaging (Lee et al., Mappingmyocardial fiber orientation using echocardiography-based shear waveimaging. IEEE Trans Med Imaging 2012; 31(3):554-62), Diffusion tensormagnetic resonance imaging (Pashakhanlo et al., Myofiber Architecture ofthe Human Atria as Revealed by Submillimeter Diffusion Tensor Imaging.Circ Arrhythm Electrophysiol. 2016; 9: e004133), or another method.

Other characteristics of the ablation target optionally include, forexample, a rate of perfusion (which tends to carry heat away from thetissue being lesioned), a rate of metabolic heat generation, and thetendency of the tissue itself to absorb heat—for example, in the case ofRF ablation, this relates to the dielectric properties of the tissue andthe frequency of the ablation field. Tissue characteristics relating tomodeled thermal properties are also discussed, for example, in relationto FIG. 10.

In some embodiments, already existing lesions (e.g., fibrotic tissue),such as from an earlier ablation procedure, are also taken into account.Optionally, such lesions are identified so that they can be incorporatedinto a new line of planned ablation. The lesions potentially also havedifferent thermal and/or dielectric characteristics which influencesimulation of ablation results.

Production of an Ablation Plan

For purposes of explanation, ablation procedure planning (corresponding,for example, to block 153 of FIG. 1A) is described herein in terms ofthe placement of the ablation path (block 118), the plan of ablationprobe movement along that path (block 120), and finally the parametersof ablation which optionally are selected to vary as the probe movesalong the path (block 122). However, it is to be understood that in someembodiments, these plan features are optionally determined togetherand/or in parallel. For example, which sub-lesion positions are optimalalong a portion of the lesion path is potentially influenced by how muchand/or with what timing lesioning energy is delivered. In someembodiments, determining a final ablation plan comprises iterativelyadjusting these plan features to approach more optimal results, and/orgenerating a selection of alternative plans from which the most optimalresult is chosen. In some embodiments, operations of blocks 118, 120 and122 in particular are carried out by application of a thermal and/ordielectric property simulation of the tissue to be treated.

Optimization of Ablation Path

At block 118 of FIG. 1B, in some embodiments, an optimal path isgenerated, based on the preliminary ablation line, and on one or more ofthe data: providing protective constraints (block 112), characterizingthe ablation target (block 116) tissue, and describing accessconstraints and conditions (block 114).

In some embodiments, the optimal path may be understood as the pathwhich best simultaneously satisfies several, potentially contradictory,constraints and/or criteria. In general, the overall ablation planpreferably seeks effectiveness of the block while protecting againstcollateral damage, and achieving the greatest speed of lesioningcompatible with these two goals. More specifically, the constraintsand/or criteria include, for example:

-   -   minimization of path length;    -   minimization of sub-lesion number;    -   minimization of complexity, required precision, and/or time of        catheter maneuvering;    -   avoidance of collateral damage to non-target tissue;    -   access to the target, dependent, for example, on anatomy shape        and/or catheter mechanics; and/or    -   features of the target anatomy, for example, tissue wall        thickness, existing lesions, and/or fiber direction.

In some embodiments, calculation of these criteria and/or conditions isperformed based on the data established and/or characterized in blocks112, 114, and/or 116. Potentially, these criteria are in at leastpartial conflict. For example, a more effective block may be achieved bya larger lesion, but a larger lesion in turn may be more likely to causecollateral damage to non-target tissue. In another example, completelyavoiding a region where collateral damage is a risk may involvecircumvention which produces an impractically long ablation line.

In some embodiments, a lesion planning and/or catheter tracking system1100 (for example, as described with respect to FIG. 11) is providedwith one or more algorithms that take criteria-characterizing input(such as the results of blocks 110, 112, 114, and/or 116) and from itgenerate an ablation plan comprising a line of planned ablation 55.Optionally, the plan also defines ablation parameters to be appliedalong the line of planned ablation 55. The one or more algorithms takeinto account criteria which the inputs have calculated, in order toproduce an optimal result under some algorithm-dependent regime of therelative influence of these criteria. Optionally, the relative influenceof criteria is adjustable by a user. Additionally or alternatively,there may be several options presented to a user (e.g., corresponding todifferent algorithms, and/or the same algorithm performed usingdifferent parameter settings). Each option is potentially optimal undera different regime of how criteria representing risks and benefits aretaken into account in planning. In particular, potentially conflictingcriteria may be balanced or reconciled, for example: by weighting, byhow an algorithm gates options and/or orders calculations consideringeach criterion, or by another method. Optionally, the user selectsand/or modifies the method used to balance and/or reconcile potentiallyconflicting criteria, e.g., using a computer's user interface.

Moreover, there is optionally a balance kept between any of thesecriteria (particularly speed) and user intent. For example, a user maypropose a preliminary line of planned ablation which is not optimal forminimal length, but which increases a user-perceived margin of errorand/or user comfort for lesion placement. Optionally, optimization ofthe line of planned ablation is performed for criteria of safety andblock, while optimization for speed is limited to parameters which donot further adjust the position of the line of planned ablation.Optionally, a user may choose to ablate along a line which follows, oris otherwise placed according to consideration of at least portions ofan existing lesion.

With respect to speed of ablation: all things being equal, it isoptionally preferable between two alternatives for the line of plannedablation to be shorter, for the number of lesions created to be fewer,and/or for the total energy delivered to be lessened. These criteria of“least ablation” are themselves potentially in partial conflict betweeneach other; e.g., if ablation plan results in fewer but largerablations, this is a potential advantage for reducing a risk ofaccidentally leaving an impulse transmission gap, even if there is acorresponding potential disadvantage in terms of time or energy requiredto create larger lesions. In some embodiments, the optimal tradeoff usedin calculation is predetermined. Optionally, however, a user ispermitted (e.g., by use of a suitable user interface) to select arelative balance of how conflicting criteria are resolved.

The line of planned ablation 55 shown in FIG. 2B is minimally disturbedfrom the preliminary line of planned ablation 54 for applying protectivecriteria, without also minimizing path length. However, reference is nowmade to FIG. 2E, which is a schematic illustration of an alternativeline of planned ablation 56, in accordance with some exemplaryembodiments of the invention. In this instance, preliminary line ofplanned ablation 54 is shown aggressively optimized for reduced lengthas alternative line of planned ablation 56. Optionally, preliminary lineof planned ablation 54 is “shrunk” until some sub-lesions producedtherealong would just reach to the limit of vein ostium protectionregions 63, 64. In some embodiments, lengthening the path byover-shrinkage is prevented; the effect is as though a rubber band wereextended between sub-lesioning which are not in direct contact with thevein ostium protection regions 63, 64.

As for the protective criteria of block 112: in FIG. 2B, line of plannedablation 55 is shown adjusted from preliminary line of planned ablation54 by diversions which pull the line centrally away from regions 61 and62 at which ablation is indicated to accompany a potential risk forcollateral damage.

Optionally, protective constraints are treated as dominant where theycome into conflict with the optimization of procedure speed. Forexample, satisfying protective criteria of block 112 optionallycomprises slowing a rate of ablation, and/or lengthening the line ofplanned ablation to avoid zones of preferable ablation exclusion. Forexample, if a preferred set of ablation parameters (e.g., a set which isoptimal for speed and transmurality as a function of tissue wallthickness) happens to violate protective constraints, then the line ofplanned ablation is optionally moved to an area where the protectiveconstraints are satisfied. Additionally or alternatively, the plan isadjusted to reduce ablation “intensity” (e.g., reduced duration,frequency, and/or power) to reduce collateral damage. For example, alonga portion of line of planned ablation 55 (within overlap region 55A),vein ostium protection region 63 slightly overlaps with tracheaprotection region 62. This leaves no apparent unimpeded path forlesioning, but routing ablation around this block would significantlyincrease the overall length of the lesion line. Reducing ablationintensity through this region is an optional way to keep the line short,while mitigating the potential for collateral tissue damage.

In some embodiments, the access constraints of block 114 establish zonesof preferable exclusion for the line of planned ablation. For example,if an ablation probe cannot mechanically reach a surface region from anassumed base position such as a transseptal entry point, then the lineof planned ablation is optionally adjusted to avoid it. Alternatively,the plan may be adjusted for use of an ablation probe with differentmechanical characteristics, different electrode positions, and/or adifferent base position.

Planning of Ablation Path Traversal

At block 120 of FIG. 1B, in some embodiments, a traversal plan of lineof planned ablation is defined. Optionally, the traversal plan takesinto account mechanical and/or spatial limitations of the positioning ofthe ablation probe. Optionally, the traversal plan is designed so thatpositioning operations which entail the greatest risk of placement errorand/or delay occur at positions where larger gaps between lesions arepotentially least likely to enable impulse propagation therethrough.

Reference is now made to FIG. 3C, which is a schematic illustrationhighlighting details of a planned set of ablations creatingsub-ablations 220 and their traversal along a line of planned ablation55, in accordance with some exemplary embodiments of the invention.

Potentially, positioning for lesioning achieved by direct movementbetween adjacent lesion foci (sub-lesions, for example) is less prone toerrors and/or delays which can introduce gaps in the ablation line thatpermit impulse transmission. However, joining between the starting andstopping points of a lesion traversal line generally requires making ajoin between sub-lesions where the later sub-lesion is formed up toseveral minutes after the earlier one. During the interval, not onlydoes the tissue tend to cool (which can reduce a degree of sub-lesionchaining described in relation to FIGS. 5A-5B), but there can also be anedematous response by the tissue which affects ablation effectiveness.In some embodiments, these effects are simulated as part of ablationplanning.

In some embodiments, a traversal plan is designed so that such joins arepositioned over regions where myocardial fiber orientation 68 (just afew patches of fiber orientation 68 are shown for illustration)generally cuts across to the direction of potential propagation acrossthe gap (fiber orientation is also discussed in relation to targetcharacterization at block 116, and with respect to FIGS. 3A-3B herein).For example, sub-lesion 310 is optionally a preferred candidate for astarting lesioning position, since the local direction of fibers meansthat sub-lesion neighbor 319 can be placed with greater error, whilestill maintaining an effective block.

Another instance where repositioning is optionally planned for is atplaces where the ablation probe reaches the end of its available travel,and must be reconfigured in order to continue along the path. An exampleof two different catheter configurations reaching the same region isshown, for example, at positions 242 and 241 of ablation probe 10 inFIG. 2D, corresponding to sub-lesions 316 and 315 of FIG. 3C. In someembodiments, where there is some overlap of the zones of travel of thetwo configurations, the break point is chosen for ease of joining up thetwo different lines. For example, advantage is taken of the reducedconstraint on positioning represented by myocardial fiber orientation atsome positions.

Planning of Sub-Lesions

At block 122 of FIG. 1B, in some embodiments, ablation parameters aredefined for sub-lesion positions along the line of planned ablation 55.Circumstances affecting planned ablation parameters include thethickness of tissue, which may vary along the extent of the line ofplanned ablation 55, the proximity of tissue prone to collateral damage(particularly the phrenic nerve 45 and the esophagus 44), the proximityof tissue which is relatively resistant to heat damage (e.g., relativelynon-heat-conductive lung tissue), the predicted relative timing oflesion placements (which may be keyed, for example, to activation of theablation catheter for lesioning), and other thermal parametersassociated with a thermal simulation of ablation, for example asdescribed in relation to FIGS. 10-13B.

Continuing reference is made to FIG. 3C. Reference is also made to FIG.2C, which is a schematic illustration in a wider anatomical context ofthe planned set of ablation sub-lesions 220 for ablating along line ofplanned ablation 55, in accordance with some exemplary embodiments ofthe invention.

It is noted that most of the sub-lesion locations marked (e.g.,sub-lesion 310) are relative large in diameter. Optionally, thisreflects a default ablation setting, wherein a full-power, full-durationablation is planned to be carried out at the given position. This may beappropriate, for example, when the tissue wall 50 is relatively thick,and there is a relatively low risk of serious collateral damage whichallows proceeding rapidly. Somewhat smaller sub-lesion sizes are shown,for example, at sub-lesion 311, and in particular through regions 312,313, and 314. In some embodiments, smaller sub-lesions are formed, forexample, by use of a lower ablation power, and/or by use of a shorterlesioning dwell time. Smaller lesions through region 312, for example,optionally reflect an increase in care to avoid damage to the esophagus(compare, for example, to the positions of ablation sub-lesions 220 inFIG. 2C relative to regions 62 and 63). Optionally, smaller lesionsthrough regions 313 and 314 reflect the presence of another constraintor condition; for example, a thinner tissue wall thickness, and/or alocally higher rate of perfusion which reduces the ability to heatnearby tissue.

Although sub-lesions 220 are drawn as abutting circles, it is to beunderstood that an ablation plan optionally overlaps sub-lesion areas tohelp ensure that deeper tissue is not subject to impulse-transmittinggaps. Optionally, sub-lesion shapes are different than circular, due,for example, to oblique angles of contact between the ablation probe 10and the tissue wall (an example of this is shown in FIGS. 13A-13B).Optionally, an ablation probe is slowly dragged across a surface,leaving a more streak-like sub-lesion. Another factor which can affectsub-lesion shape is the interaction between heating delivered atdifferent sub-lesion locations.

Reference is now made to FIGS. 5A-5B, which schematically illustrateplanning for adjacency effects of tissue lesions 501, 502, 503 made intwo different sequences, in accordance with some exemplary embodimentsof the invention.

A superficial extent of sub-lesion 501 is represented by the outercircle, while progressively smaller interior circles 501A, 501B, 501Crepresent lesion extent at gradually increasing depths (depth issimilarly represented for sub-lesions 502 and 503). In some embodiments,after a first lesion 501 is made, a second lesion 502 is made only afterthe elapse of a cool-down period. Then the two lesions potentially aremade as if independent from one another. Unless care is taken to ensuresufficient overlap, this can increase the potential for animpulse-permissive gap, particularly in the deeper layers.

In FIG. 5B, however, sub-lesion 503 is placed almost immediately aftercreation of lesion 501, while there remains some residual heating fromthe previous ablation. In this case, thermal simulation may show thatthe two sub-lesions will tend to merge, for example as shown at region505. In some embodiments, an ablation plan reflects assumptions abouthow quickly heating at each planned position for creating a sub-lesioncan begin (optionally, it begins effectively immediately when a draggingtechnique is used). This provides potential advantages both for creatinggap-free transmural lesions, and for increasing the speed with whichlesions can be formed.

Optionally, the ablation effect of a first sub-lesion may be simulatedas well. For example, residual heating and/or lesioning effects ontissue parameters are optionally inputs to a simulation of a secondsub-lesion ablation (for example, one made in tissue sufficiently nearto the first sub-lesion to be potentially affected). Optionally, suchsimulation facilitates defining the sub-lesioning sequence; e.g., theorder and/or timing by which sub-lesions are ablated.

Reference is now made to FIGS. 7A-7C, which illustrate the 3-D displayof a lesion plan for a left atrium 700, in accordance with someexemplary embodiments of the invention.

In some embodiments, the results of lesion planning are shown to a userby use of a 3-D display. FIGS. 7A-7C illustrate one such plan display. A3-D model of a left atrium 700 (porcine, in this example) is shown fromthree viewpoints. Sub-lesion loci are indicated by the trails of darkmarks 701 (modeled as embedded spheres, for example). In this case, thelesion lines are shown extending around portions of the roots of theinferior vena cava 48.

Application and Dynamic Adaptation of an Ablation Plan

Reference is now made to FIG. 6, which schematically illustrates amethod of real-time use, with optional adjustment, of an ablation plan,in accordance with some exemplary embodiments of the invention.Reference is also made to FIG. 8A, which illustrates the 3-D display ofa planned lesion ablation line for a left atrium 800, along with anablation probe 10, in accordance with some exemplary embodiments of theinvention. Reference is further made to FIG. 8B, which illustrates aninterior 3-D view of left atrium 800, probe 10, and planned ablationline 802, in accordance with some exemplary embodiments of theinvention.

In some embodiments, a line of planned ablation 802, together withparameters of planned sub-lesions 220 is used during a procedure bycombining measured ablation probe positions within the body with cues toguide operation of the ablation probe so that the previously determinedablation plan is followed.

The flowchart begins (after production of an ablation plan, for exampleby the methods of FIGS. 1A and/or 1B), and at block 130, in someembodiments, a portion of a planned lesion is made (e.g., a sub-lesioncomprising ablation from a fixed ablation probe location, or adragged-out portion of a lesion). Optionally, the lesion is made inconjunction with visual guidance provided to the user, for example,visual guidance as shown in FIGS. 8A-8B. In FIG. 8A, visual guidance ispresented from an outside-the-heart point of view. In FIG. 8B, the pointof view is that of the ablation catheter itself, shown as if from withina heart chamber emptied of blood. Optionally, as the actual ablationprobe is moved, its motions (measured, for example, by system 1100 ofFIG. 11) are shown also in a live presentation of the views of FIG. 8Aand/or FIG. 8B. In some embodiments, the display is adjusted to alsoinclude anatomically realistic tissue coloring and/or responsiveness toablation probe contact and/or to the effects of ablation itself.

Optionally, selection of pre-planned ablation parameters isautomatically made when an ablation probe approaches the next plannedlesion position. Optionally, the system guides the user to the nextplanned lesion position. Optionally, a user is provided with aninterface which allows modifying or overriding these settings.

In some embodiments, the system adapts the ablation plan to actualevents during ablation, for example, as now described in relation toblocks 132, 134, 136, 138, and 140.

At block 132, in some embodiments, the system 1100 characterizesparameters such as ablation probe position and settings of the actualablation operation performed (optionally, the ablation operation set tobe performed based on the current ablation probe position and settings).Optionally, information about the ablation probe position includes acontact force or other assessment of contact quality (e.g. dielectricproperty contact quality assessment) between the ablation probe andtarget tissue. Optionally, the new state of tissue in the lesionedregion is modeled, based on actual ablation position and parameters, andon data previously configured for thermal simulation. Additionally oralternatively, at block 134, in some embodiments, the lesion actuallycreated is itself characterized, for example, by the analysis ofdielectric measurements and/or temperature readings.

At block 136, in some embodiments, a determination is made as to whetheror not the plan is still being followed as currently defined. If so,flow continues at block 140.

Otherwise, at block 138, in some embodiments, the lesion plan isadjusted. Adjustment may be made in any parameter of the lesion plan toadjust, for example: to a deviation from the previously planned timingand/or placement of sub-lesions, to a deviation from an expected effectof a lesioning operation (as measured, for example, from dielectricmeasurements of lesion extent), and/or for a deviation from an expectedpre-lesion tissue state (for example, an expected pre-existing lesion isfound to be of a different extent; measured, for example, by dielectricmeasurements and/or measurements to assess functional blockage ofimpulse transmission).

For example, if a sub-lesion was placed with too large a gap between itand an adjacent sub-region, the plan may be adjusted to fill in the gapregion. In another example, if more time has passed between sub-lesionsthan the current plan anticipates (such that there has been too muchcooling in the interim), the recommended placement of the nextsub-lesion is brought closer to the previous lesion.

The lesion plan is optionally be adjusted in accordance with any of themethods described in FIG. 1A or 1B. The actual measured parameters(e.g., as measured in blocks 132 or 134) are optionally inputted to thesimulation in order to adjust the lesion plan.

At block 140, in some embodiments, a determination is made as to whetheror not the lesion plan has been adequately completed (e.g., according tocompletion of the planned sequence of steps, and/or based onverification measurements of the actual lesion). If not, the flowchartreturns to block 130. Otherwise, the flowchart ends.

Systems and Methods for Thermal Simulation of Tissue Ablation Referenceis now made to FIG. 10, which is a schematic flowchart of a method forgenerating a tissue simulation including thermal and dielectricproperties, in accordance with some embodiments of the presentinvention. Concurrent reference is also made to FIG. 11, which is ablock diagram of components of a system for tracking the position of anintra-body catheter, which is also optionally configured as a system forlesion planning, in accordance with some embodiments of the presentinvention.

In some embodiments, the method receives a dataset representing ananatomical image (e.g., 3-D CT images) of the patient, and based ondielectric properties of tissue types (e.g., impedance and/orconductivity) and/or thermal properties (e.g., thermal conductivity,heat capacity, and metabolic heat generation) identified within theanatomical image, creates a dielectric map and/or a thermal map (i.e.,dataset) for the patient. The dielectric and/or thermal map is used as abasis for a generating a simulation of lesioning along a line of plannedablation during a simulated procedure. The output of the simulation isused to predict ablation procedure effects on actual tissue; forexample, ablation using an RF ablation catheter.

In some embodiments, modeled thermal parameters include thermalproperties general to animate or inanimate matter, for example, thermalconductivity and/or heat capacity; and/or thermal properties specific tobiological tissues, for example, metabolic heat generation, absorptionrate, and/or blood perfusion rate. Optionally, the thermal propertiesare used as inputs into a bio heat formulation of a heat equation toestimate temperature evolution in the region of interest as a functionof time and/or space.

In some embodiments, electric and/or dielectric parameter values areassociated with the thermal parameter values. Optionally, the electricand/or dielectric properties are temperature and/or frequency dependent.Optionally, estimation of the dielectric parameter values includessimulating temperature-dependent dielectric parameter effects of thethermal parameters, and/or measuring and/or calculating the thermalparameters in real time.

Other inputs to the simulation optionally include data about theablation probe 10, for example, its shape, mechanical characteristics ofits maneuverability, and simulated position. In some embodiments,parameters of ablation power delivery are also provided as inputs: forexample, frequency, power, duration of use, duty cycle, and/or phases ofdelivery through different electrodes.

In some embodiments, the system of FIG. 11 allows for an operator tomonitor progress of an intra-body procedure according to a treatmentplan, for example, lesioning along a line of planned ablation, withsufficient accuracy and precision to allow monitoring actual vs. plannedablations. Optionally, the system is configured to dynamically adjustthe treatment plan according to the progress of the procedure. Thesystem of FIG. 11 may execute, for example, the method of FIGS. 1A-1Band/or 10 (during a planning phase of a procedure); and/or FIG. 6(during the procedure itself).

It is noted that the system of FIG. 11 may correct the location of thedistal end of the catheter by separately and substantiallysimultaneously tracking the position of sensors, electrodes and/or otherconducting ports on the distal end of the catheter.

As used herein, the terms sensor and electrode are sometimesinterchangeable, for example, where referring to an element thatperforms measurements of one or more electrical properties (e.g.,dielectric properties, conductance, impedance, voltage, current, and/orelectrical field strength). For example, the electrodes may function asthe sensors, such as by transmitting from one electrode to a secondelectrode, where the second electrode functions as a sensor. Impedancemay be measured between respective electrode pairs, and/or between adesignated electrode and a reference electrode (which may be locatedoutside the body and/or within the body, such as on the catheter).

The system of FIG. 11 may provide additional features, for example,selection of the dielectric and/or thermal parameters (and/or elementsthat generate the dielectric and/or thermal parameters); estimation ofcontact force applied by the distal end of the catheter to the tissuewall, estimation of the lesion formation (e.g., size, volume and/ordepth), estimation of tissue temperature, and/or mapping of fibroticregions.

System 1100 may include a program store 1106 storing code, and aprocessor 1104 coupled to program store 1106 for implementing the storedcode. Optionally, more than one processor may be used. It is noted thatprogram store 1106 may be located locally and/or remotely (e.g., at aremote server and/or computing cloud), with code optionally downloadedfrom the remote location to the local location for local execution (orcode may be entirely or partially executed remotely).

System 1100 may include an imaging interface 1110 for communicating withone or more anatomical imaging modalities 1111 that acquire a dataset ofimaging data of a patient, for example, anatomical imaging data, e.g., acomputer tomography (CT) machine, an ultrasound machine (US), a nuclearmagnetic resonance (NM) machine, a single photon emission computedtomography (SPECT) machine, a magnetic resonance imaging (MRI) machine,and/or other structural and/or functional anatomical imaging modalitymachines. Optionally, imaging modality 1111 acquires three dimensional(3-D) data and/or 2-D data. It is noted that the anatomical images maybe derived and/or acquired from functional images, for example, fromfunctional images from an NM machine.

System 1100 may include an output interface 1130 for communicating witha display 1132, for example, a screen or a touch screen. Optionally,physically tracked location coordinates are displayed within apresentation of the dataset; for example, the 3-D acquired anatomicalimages are displayed on display 1132, with a simulation of the locationof the distal end of the catheter within the displayed image based onthe corrected location (examples of this are shown in FIGS. 8A-8B).

System 1100 may include an electrode interface 1112 for communicatingwith a plurality of physical electrodes 1114 and/or sensors (optionally,the electrodes serve as the sensors) located on a distal end portion ofa physical catheter 1116 designed for intra-body navigation; forexample: an electrophysiology (EP) ablation catheter, and/or anotherablation catheter (e.g., a chemical ablation or injection catheter).Alternatively or additionally, system 1100 includes a navigationinterface 1134 for communicating with a catheter navigation system 1136;optionally a non-fluoroscopic navigation system; optionally, animpedance measurement based system.

In some embodiments, intra-body navigation is performed based on bodysurface electrodes that receive and/or transmit current (e.g.,alternating current) in different frequencies and/or different timesbetween co-planar directions. Analysis of the electrical and/or thermalparameters obtained from the sensors of the catheter, separated into thedifferent channels, is optionally used to estimate the location of eachsensor relative to each body surface electrode. A calibration of thedistances between the sensors (e.g., based on manufacturingspecifications of the catheter, and/or measurements such as usingfluoroscopy or other methods) may be performed.

Optionally, system 1100 includes a sensor interface 1126 forcommunicating with one or more sensors 1128, which may be in the body orexternal to the body; for example, for measuring electrical and/orthermal parameters, for example, impedance and/or conductivity and/orthermal conductivity and/or heat capacity and/or metabolic heatgeneration of the blood, the myocardium, and/or other tissues.

Optionally, system 1100 includes a data interface 1118, forcommunicating with a data server 1122, directly or over a network 1120,to acquire estimated dielectric and/or thermal tissue values forassociation with the acquired imaging dataset. Alternatively, theestimated dielectric and/or thermal values are stored locally, forexample, on data repository 1108.

Optionally, a user interface 1124 is in communication with datainterface 1118, for example, a touch screen, a mouse, a keyboard, and/ora microphone with voice recognition software.

Optionally, system 1100 (e.g., computing unit 1102) includes a connector1140 connecting between catheter 1116 (e.g., RF ablation catheter,injection catheter) and a connector interface 1142 (and/or electrodeinterface 1112). Connector 1140 may be used to add additional featuresto existing catheters, such as off the shelf catheters, for example, RFablation catheters, at least by acting as an input of signalscommunicated by the catheter for processing by system 1100. The signalscommunicated by the catheter are intercepted by circuitry withinconnector 1140 and transmitted to interface 1142 and/or 1112, withoutinterfering with the signal transmission. The intercepted signals may beanalyzed by system 1100, for example, to perform real-time tissuemeasurements (e.g., contact force, pressure, ablated volume and/ordepth, temperature, and/or fibrosis mapping), to perform localization ofthe catheter, and/or to identify the type of the catheter.

It is noted that one or more of interfaces 1110, 1118, 1112, 1126, 1130,1134, 1142 may be implemented, for example, as a physical interface(e.g., cable interface), and/or as a virtual interface (e.g.,application programming interface). The interfaces may each beimplemented separately, or multiple (e.g., a group or all) interfacesmay be implemented as a single interface.

Processor 1104 may be coupled to one or more of program store 1106, datarepository 1108, and interfaces 1110, 1118, 1112, 1126, 1130, 1134,1142.

Optionally, system 1100 includes a data repository 1108, for example,for storing the dataset (e.g., imaging data of a patient), thesimulation, received electrical and/or thermal parameters, and/or otherdata (such as: health record of a patient). The data may be displayed toa user (e.g., physician) before, during and after the procedure.

It is noted that one or more of processor 1104, program store 1106, datarepository 1108, and interfaces 1110, 1118, 1112, 1126, 1130, 1134, 1142may be implemented as a computing unit 1102, for example, as astand-alone computer, as a hardware card (or chip) implemented within anexisting computer (e.g., catheterization laboratory computer), and/or asa computer program product loaded within the existing computer.

Program store 1106 optionally includes code implementable by processor1104 that represents a simulation tool and/or application that generatesRF simulations (e.g., based on simulated generated fields) based on aprovided dielectric map and/or other data.

Returning to FIG. 10: at 1002, a dataset of a body portion of a patientincluding anatomical imaging data of the patient (optionally 3-D data)is provided, for example, acquired from imaging modality 1111 (e.g., CT,MRI), retrieved from repository 1108, and/or acquired from an externalserver or other storage. Alternatively or additionally, the dataset isacquired and/or derived from a functional imaging modality, for example,NM and/or SPECT. For example, data from the NM modality may be used toinfer the location of autonomous nervous system components (e.g., one ormore ganglion plexi) designated for treatment on the dataset from the CTmodality, for example, as described with reference to “BODY STRUCTUREIMAGING”, International Publication No. WO2014/115148 filed Jan. 24,2014, which is incorporated herein by reference in its entirety.

The data obtained from the CT machine (and/or other imaging devices)serves as a basis for geometrical structure and/or modeling of internalorgans of the patient, for example, the organs are segmented using imagesegmentation code. The electrical and/or thermal properties and/or othervalues (e.g., mechanical, physiologic, other tissue related values) areassociated with each organ, optionally according to the designatedoperational frequency used by the RF ablation catheter.

Optionally, the imaging dataset includes the target tissue for treatmentin a catheterization procedure; for example, the heart. Optionally, theimaging dataset includes tissues surrounding the target tissue forsimulation of the procedure, for example, a full body scan, a fullthorax scan, a chest and abdominal scan, and/or a chest scan. Forexample, for an intra-cardiac ablation procedure, a full thorax scan maybe performed.

Optionally, the imaging data is analyzed and/or processed to identifydifferent types of tissues within the imaging data, for example, eachpixel data or region is classified into a tissue type. Suitableclassification methods include, for example, according to imagesegmentation methods, according to a predefined imaging atlas, and/orbased on Hounsfield units.

Code stored, for example in program store 1106, implementable byprocessor 1104 accesses estimated dielectric and/or thermal parametervalues, and associates each tissue type and/or pixel and/or region inthe dataset with the estimated dielectric and/or thermal parametervalues.

The dielectric and/or thermal parameter values may be obtained, forexample, from a publicly available database (e.g., on data server 1122),calculated from a model, and/or based on empirically measured valuesfrom a sample of patients. It is noted that the estimated dielectricand/or thermal parameter values may reflect values that have notnecessarily been measured for the patient being treated. In someembodiments, a 2-D or 3-D dielectric map of the region (e.g., organ) ora portion of the organ is created and optionally displayed to a user.

The dataset including anatomical image data associated with thedielectric and/or thermal parameter values may sometimes be referred toherein as a dielectric map. It is noted that the dielectric map mayinclude dependencies of the dielectric parameter values on the thermalparameter values.

Optionally, the anatomical image (e.g., after segmentation) and theestimated dielectric and/or thermal parameter values or the 2-D or 3-Ddielectric map are inputted to the simulation tool, which may beimplemented as code stored in program store 1106 implementable byprocessor 1104, or as a separate unit (e.g., external server, hardwarecard, remotely located code implementable locally).

Optionally, the dataset is used to generate a simulation as part of apre-planning phase, for example, as described with reference to FIGS.1A-1B. The pre-planning phase simulates different parameters for theplanned procedure, to help select one or more different parameters forthe actual procedure, according to, for example, reduced error intracking the location of the catheter, improved accuracy in trackinglocation of the catheter, selection of the treatment location of thecatheter, and/or selection of ablation parameters and/or ablation linesaccording to a simulation of the ablation.

Optionally, the dielectric parameters include an impedance and/orconductive value of the respective tissue and/or tissue region.Optionally, information used in the simulation includes a contact forceor other measure of contact (e.g. dielectric property contact qualityassessment) between the ablation probe and target tissue.

It is noted that the patient may undergo imaging before thecatheterization procedure, for example, as a separate outpatientprocedure.

Optionally, the dataset after simulation is revised to include theimaging data and the one or more dielectric and/or thermal parametervalues corresponding to different tissues and/or regions of theanatomical imaging data. The dielectric and/or thermal parameter valuerepresents an initial estimated value, which may be adjusted based onreal-time measurements obtained from the patient.

Optionally, the dataset is associated with additional data, for example,mechanical parameters (e.g., fibrosis map), physiological parameters(e.g., patient ECG patterns, patient body temperature), myocardial fiberorientation data, heart wall thickness data, and other tissue specificparameters. In some embodiments, the data set comprises characterizationof an anisotropy of the tissue, for example, a structural anisotropysuch as myocardial or other fiber orientation, and/or a functionalanisotropy such as direction of perfusion and/or impulse propagation.

Optionally, the dataset is associated with additional data related tothe medical state of the patient; for example, medications the patientis taking (e.g., which may affect the ionic concentration of the tissuesof the patient, affecting the electrical and/or thermal parameters), themedical state of the patient (e.g., which may affect the anatomy of thepatient), and a history of previous treatments (e.g., which may helppredict the effects of the current treatment).

At block 1004 of FIG. 10, in some embodiments, code stored in datarepository 1108 processes the dielectric map (i.e., the dataset) ofblock 1002, to generate a simulation. In some embodiments, thesimulation simulates the navigation path during the procedure or partthereof, using a simulated catheter, and simulated applied electricparameters by simulated body surface electrodes (e.g., positioned on theskin of the patient).

Optionally, the simulation receives one or more of the following inputs,to generate the initial simulation and/or update the simulation (e.g.,as in block 134 of FIG. 6): the anatomical model (e.g., obtained basedon a CT and/or other imaging data of the patient), the dielectric map(initial or updated) which includes dielectric properties and/or thermalproperties, fibrosis data, conductance map (e.g., from a stored locationbased on previous conductance mapping and/or real-time mapping),ablation catheter parameters (e.g., frequency, model, type, mechanicalmaneuvering properties, and/or electrodes positions), impedancemeasurements, thermal property measurements, and/or other data values.

The simulation may track the position (such as coordinates) of thesimulated catheter within the dataset representing the body portionaccording to the simulated application of the electrical fields (orother electrical parameters, such as current, impedance, and/or voltage)within the body portion (i.e. based on the extra-body simulatedelectrodes). The simulation may simulate the measurements of thesimulated applied electrical fields, optionally as measured byelectrodes at a distal portion of the simulated catheter. In particular,the simulation may track thermal effects of the application of ablationenergies to portions of the body visited by the catheter.

Optionally, the generated simulation includes a dataset of thecoordinates (or other position data) of the simulated catheter withinthe dataset related to navigation of the catheter as part of theprocedure.

Optionally, the simulation is performed at one or more operatingfrequencies, for example, when simulating a catheter ablation procedure.Exemplary simulation frequencies include: about 460 kilohertz (kHz),about 1 megahertz (MHz), about 12.8 kHz, or other frequencies. Thesimulation frequency is used to measure changes during the ablationprocess, and correct the ablation parameters accordingly, as describedherein.

Optionally, the simulation includes coordinates in space which representa simulation of electrodes and/or sensors that provide measurements ofvalues of the electrical and/or thermal properties. The simulation ofthe measured values may be used, for example to simulate the measurementof induced currents. The simulation of the induced currents may reducethe number of time the simulation is run to below the number of samplingpoints in space, which reduces the required computational resources toperform the simulation.

Optionally, the simulation calculates the optimal position for amulti-electrode phased RF catheter, for example, to obtain the bestreal-time measurements, for example, with improved signal to noise, orreduced error.

Exemplary commercially available simulation tools that may be used as aframework for generating the simulation described herein include:Sim4Life (available from Zurich Med Tech), COMSOL Multiphysics®, and CSTDesign Studio™.

Reference is now made to FIG. 12, which is a flowchart of an exemplarymethod for generating the thermal component of the generated simulation,in accordance with some embodiments of the present invention.

The flowchart begins, and at block 1210, in some embodiments, theelectric properties of the catheterization procedure materials are setbased on the received values, for example, for a certain catheter, at acertain angle, pressure, and operating frequency (e.g., when performingan ablation procedure and/or as part of a measurement process). Thesimulation is generated to simulate the electromagnetic fields on thecatheter. The power density loss (PLD) pattern is optionally simulated.

At block 1212, in some embodiments, the thermal properties of thetissues and/or catheterization procedure are set based on the receivedvalues. The PLD pattern is optionally used as a heat source forgenerating the thermal property component of the generated simulation.The thermal properties are simulated over a period of time to obtain atemperature distribution pattern over the period of time; for example,based on the procedure. The period of time may represent a significantperiod of time, for example, based on cardiac output, based on theestimated time to navigate the catheter within the heart, and/or basedon the time for performing an ablation.

The initial electrical and thermal property values are updated as afunction of temperature based on the initial simulation. At block 1214,in some embodiments, a determination is made as to whether thesimulation period is complete or not. If not, blocks 1210 and 1212 areiterated over again. Otherwise, the flowchart ends. The blocks may beiterated until a stop condition is met, for example, a desired accuracyand/or simulation time, and/or until the values remain unchanged withina tolerance requirement. Optionally, during each iteration, thesimulation uses the values calculated using the earlier simulation, toimprove the accuracy and/or resolution of the updated simulated values.

Referring now back to block 1004 of FIG. 10: optionally, the generatedsimulation includes determination of a power loss density pattern. ThePLD pattern may be generated for the tissue targeted for (or currentlybeing) treated using RF energy. The PLD pattern may be estimated in timeand/or space. Alternatively or additionally, the simulation includesdetermination of a temperature pattern. The temperature pattern may begenerated for the tissue targeted or (or currently being) treated usingRF energy. The PLD pattern may be estimated in time and/or space. ThePLD pattern may be calculated for multiple points, for each set ofelectrode location (e.g., using the coordinates according to theexternally applied electromagnetic field), the pressured applied to thetissue wall, and the angle of the electrode relative to the tissue. ThePLD pattern may be used in the generated simulation to guide theablation treatment.

The PLD pattern, and/or gasification transition pattern, and/ortemperature pattern may be used to update the simulated electric fieldsfor correction of coordinates determined using real-time measurements ofthe externally applied electric fields. The PLD pattern, and/orgasification transition pattern, and/or temperature pattern may affectthe electric and/or thermal properties of tissues, which may alter thereal-time measurements of the electric field and/or real-timemeasurements of the dielectric, electric, and/or thermal properties.

The PLD pattern, and/or gasification transition pattern, and/ortemperature pattern calculated as part of the generated simulation mayuse the corrected catheter coordinates (and/or simulated cathetercoordinates, and/or measured catheter coordinates) as input of thelocation of the catheter.

The PLD pattern may be calculated using Equ. 1:

PLD=½(σ+ωε₀ε″)|E| ²=½σ_(e) |E| ²  (Equ. 1)

where:|E| is the magnitude of E;ω=2πf where f denotes frequency in Hertz (Hz); andσ_(e) is an effective conductivity defined as σ+ωε₀ε_(e)″.

The temperature pattern may be calculated based on an estimation of therise of temperature, which may be estimated according to the continuityequation (i.e., Equ. 2) that describes the simple case ofelectromagnetic heating where the temperature rises at a uniform rate:

$\begin{matrix}{\frac{\partial T}{\partial t} = \frac{PLD}{\rho c_{P}}} & \left( {{Equ}.\mspace{14mu} 2} \right)\end{matrix}$

where:ρ denotes the density; andc_(P) denotes the specific heat.

Reference is now made to FIG. 13A, which is a graph depicting thecalculated PLD pattern created by an electrode 1302 (e.g., RF ablationelectrode(s)) in a tissue 1304, in accordance with some embodiments ofthe present invention. The PLD pattern may be calculated using Equ. 1.The PLD pattern may be used in the generated simulation describedherein.

In the figure:

-   -   D denotes the ablation depth (in mm),    -   G denotes the gap between the end of the ablated depth and the        opposite wall (in mm; generally, D+G represents the wall        thickness of the tissue),    -   V denotes the volume of ablated shape in mm³. The top view of an        exemplary ablation region may be modeled as an approximately        elliptical shape, and the ablated volume as an approximate        half-ellipsoid.

The ablation volume may be further denoted by:

-   -   L denoting the length in mm of the ablation region (e.g., one        axis of the ellipsoid), and        W denoting the width in mm of the ablation region (e.g., another        axis of the ellipsoid).

Reference is now made to FIG. 13B, which is a graph depicting thecalculated temperature pattern (in degrees Celsius) created by anelectrode 1306 (e.g., RF ablation electrode(s)) in a tissue 1308, inaccordance with some embodiments of the present invention. Thetemperature pattern may be calculated using Equ. 2. The temperaturepattern may be used in the generated simulation described herein.

Optionally, the Gasification Transition (GS) of ablation using cryogenicenergy at each possible ablation region is calculated. The GS may becalculated based on the location of each ablation region, the pressure,the angle of the catheter, and/or other values. Based on the generatedsimulation, the location, pressure, angle, and/or other values may beselected to achieve safe GS values, for example, according to a safetyrequirement.

Software Modules for Ablation Planning

Reference is now made to FIG. 14, which is a schematic representation ofsoftware modules and associated data for use in ablation planning,according to some exemplary embodiments of the invention.

In some embodiments of the invention, software for ablation planningcomprises an initial planning module 1400, and/or an adaptive planningmodule 1450. In some embodiments, initial planning module 1400 isconfigured to carry out operations of flowchart FIG. 1B. In someembodiments, adaptive planning module 1450 is configured to carry outoperations of flowchart FIG. 6. In some embodiments, data block 1401corresponds to data defining a preliminary ablation line as in block 110of FIG. 1B. In some embodiments, data blocks 1402, 1403, and 1404correspond to data used in the operations of blocks 116, 112, and 114 ofFIG. 1B.

In some embodiments, initial planning module 1400 comprises an ablationsimulator, configured to receive data describing ablation properties ofthe patient-specific anatomy 1402, along with parameters of a candidateablation plan 1405 (optionally supplemented by user input 1409B), anddetermine how the ablation plan will affect tissue of the patient. Itshould be understood that user input 1409B optionally influences theoperation of any of the software modules of planning module 1400.

In some embodiments, ablation line candidate generator 1430 generates acandidate ablation plan 1405, based at least initially on target lesionindication 1401, and optionally on effects and/or constraints calculatedby one or more of software modules 1410, 1415, 1420, and/or 1425.

In some embodiments, ablation simulator 1410 carries out simulation ofthe effects of a candidate ablation plan 1405 (optionally all at onceand/or piecewise), based, for example, on thermal and/or dielectricsimulation of ablation plan effects on patient anatomy and itsproperties with respect to ablation described by data block 1402.

In some embodiments, a lesion therapeutic effect validator 1415 isprovided, which validates the degree to which simulated effects willmeet the therapeutic goals of the planned therapy (based, for example,on the ablation properties of the patient-specific anatomy 1402).Examples of these goals (e.g. transmurality and avoidance of gaps) aredescribed, for example, in relation to planning operations of FIG. 1B.

In some embodiments, a collateral damage analyzer 1420 is provided,which is configured to assess the potential for collateral damage of acandidate ablation plan 1405 (optionally, to provide suggestedalternatives to the software system which reduce a risk for suchdamage), based on awareness of vulnerable collateral anatomy provided bydata block 1403.

In some embodiments, access constraint analyzer 1425 is provided, whichis configured to assess access constraints of a candidate ablation plan1405 as being possible (for example, using a particular catheter andanatomical access route), relatively easy or hard, relatively reliableto perform, or otherwise evaluated. Optionally, access constraintanalyzer 1425 is configured to provide suggested alternative ablationplan options to the software system which provide more preferred accessto areas targeted for lesioning.

In some embodiments, the output of initial planning module 1400comprises an initial version of current ablation plan 1406 (features ofablation plans are described, for example, in relation to FIGS. 1A-1Bherein), which in turn serves as input to adaptive planning module 1450.

With reference now to adaptive planning module 1450: during a procedurefor catheter ablation, in some embodiments, ablation simulator 1411receives ablation tracking data 1407, including, for example positionsof an ablation catheter, and/or data regarding operation of the ablationcatheter. Optionally, ablation simulators 1411 and 1410 are implementedas the same module.

It should be understood that operations of the adaptive planning module1400 are optionally monitored via status indications 1408 (e.g.,displayed information) produced by the adaptive planning module 1400and/or any of its subcomponents 1455, 1460, 1465. It should beunderstood that user inputs 1409A are optionally available to modify anysuitable processing parameter and/or result produced by planning module1400 and/or any of its subcomponents.

In some embodiments, ablation progress comparator 1430 receives thecurrent ablation plan 1406, as well as ablation tracking data 1407and/or simulated ablation information from ablation simulator 1411.Comparison of the actual record of events (from tracking data 1407),and/or the simulated effects of those events (from the ablationsimulator 1411) is made to the current ablation plan 1406.

In cases where there are differences, in some embodiments, ablation planreviser 1430 assesses what if anything, should be changed in the plan inorder to achieve a successful result. Optionally, ablation plan reviser1430 effectively comprises an implementation of initial planning module1400 (and its inputs), suitably changed to support dynamic adaptation ofthe plan (e.g., allowing partial plan modifications, limiting modelingto what can be achieved in real time, etc.). In some embodiments, anupdated plan becomes the new current ablation plan 1406. Optionally, theprocess of monitoring, comparing, and revising is iteratively performed.

As used herein with reference to quantity or value, the term “about”means “within ±10% of”.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean: “including but not limited to”.

The term “consisting of” means: “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

The words “example” and “exemplary” are used herein to mean “serving asan example, instance or illustration”. Any embodiment described as an“example” or “exemplary” is not necessarily to be construed as preferredor advantageous over other embodiments and/or to exclude theincorporation of features from other embodiments.

The word “optionally” is used herein to mean “is provided in someembodiments and not provided in other embodiments”. Any particularembodiment of the invention may include a plurality of “optional”features except insofar as such features conflict.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical, pharmacological, biological,biochemical and medical arts.

As used herein, the term “treating” includes abrogating, substantiallyinhibiting, slowing or reversing the progression of a condition,substantially ameliorating clinical or aesthetical symptoms of acondition or substantially preventing the appearance of clinical oraesthetical symptoms of a condition.

Throughout this application, embodiments of this invention may bepresented with reference to a range format. It should be understood thatthe description in range format is merely for convenience and brevityand should not be construed as an inflexible limitation on the scope ofthe invention. Accordingly, the description of a range should beconsidered to have specifically disclosed all the possible subranges aswell as individual numerical values within that range. For example,description of a range such as “from 1 to 6” should be considered tohave specifically disclosed subranges such as “from 1 to 3”, “from 1 to4”, “from 1 to 5”, “from 2 to 4”, “from 2 to 6”, “from 3 to 6”, etc.; aswell as individual numbers within that range, for example, 1, 2, 3, 4,5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein (for example “10-15”, “10to 15”, or any pair of numbers linked by these another such rangeindication), it is meant to include any number (fractional or integral)within the indicated range limits, including the range limits, unlessthe context clearly dictates otherwise. The phrases“range/ranging/ranges between” a first indicate number and a secondindicate number and “range/ranging/ranges from” a first indicate number“to”, “up to”, “until” or “through” (or another such range-indicatingterm) a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numbers therebetween.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

It is the intent of the Applicant(s) that all publications, patents andpatent applications referred to in this specification are to beincorporated in their entirety by reference into the specification, asif each individual publication, patent or patent application wasspecifically and individually noted when referenced that it is to beincorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present invention. To the extent that section headings are used,they should not be construed as necessarily limiting. In addition, anypriority document(s) of this application is/are hereby incorporatedherein by reference in its/their entirety.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

What is claimed is:
 1. A method for planning an ablation plan of atarget tissue in a patient, the method comprising: receiving datacharacterizing patient-specific anatomy comprising at least the targettissue, wherein the data include data on dielectric propertiesassociated with the target tissue; simulating, by computer, one or moreoperations to lesion the target tissue, based on the received data, tocreate simulated results; evaluating, by a computer, one or morecriteria on said simulated results, said one or more criteria includinga criterion to block abnormal cardiac tissue conduction; producing, bycomputer, a planned target form of the lesion, wherein the plannedtarget form is produced based on said evaluating; producing, bycomputer, an ablation plan for producing the planned target form, theablation plan comprising parameters of ablation; and providing anindication of the planned target form.
 2. The method of claim 1, whereinthe data include data on thermal properties associated with the targettissue.
 3. The method of claim 1, wherein the received data characterizegeometry of the target tissue.
 4. The method of claim 1, wherein thereceived data characterize a structural anisotropy as a function ofposition in the target tissue, and the ablation plan is produced basedon consideration of the structural anisotropy.
 5. The method of claim 4,wherein the anisotropy comprises an orientation of myocardial fibers inthe target tissue.
 6. The method of claim 1, wherein the received datacharacterize a position of at least one existing lesion in the targettissue, and the planned target form is adjusted to incorporate the atleast one existing lesion.
 7. The method of claim 1, wherein the createdsimulated results indicate lesion effects on non-target tissue.
 8. Themethod of claim 1, wherein the ablation plan comprises parameters ofablation as a function of structure thickness along the planned targetform.
 9. The method of claim 7, wherein the target tissue comprises awall of an atrial heart chamber, and the planned target form of thelesion is produced for the blockage of cardiac muscle contractileimpulses contributing to atrial fibrillation, based on the computersimulated results of one or more operations to lesion the target tissue.10. The method of claim 1, wherein the simulated results comprisethermal simulation of the effect of lesioning on the patient-specificanatomy, based on thermal characteristics associated with thepatient-specific anatomy.
 11. The method of claim 1, wherein the plannedtarget form of the lesion is produced for transmural ablation of thetarget tissue, while avoiding collateral damage to tissue in thermalcontact with the target tissue.
 12. The method of claim 1, wherein thesimulated results comprise dielectric simulation of the effect oflesioning on the patient-specific anatomy, based on dielectricproperties associated with the patient-specific anatomy.
 13. The methodof claim 1, wherein the target tissue comprises cardiac tissue and thenon-target tissue comprises non-cardiac tissue.
 14. The method of claim1, comprising automatically adjusting the planned target form to avoidlesioning of the non-target tissue.
 15. The method of claim 13, whereinthe non-target tissue comprises at least one from the group consistingof: a portion of an esophagus, a portion of a phrenic nerve, and portionof a vascular root.
 16. The method of claim 1, wherein the simulatingproduces simulated results simulating positions of a catheter used toperform the catheter ablation; and wherein the planned target form isproduced based on regions of the target tissue which are accessible bythe simulated positions.
 17. The method of claim 16, wherein thesimulated positions are constrained by mechanical properties of thecatheter.
 18. The method of claim 16, wherein the simulated positionsare constrained by an anchor position applied to a portion of thecatheter.
 19. The method of claim 1, wherein the received data comprises3-D imaging data of the patient-specific anatomy.
 20. The method ofclaim 1, wherein said planned target form of the lesion is produced byselection.
 21. The method of claim 1, comprising automatically modifyingsaid one or more operations in response to said evaluating and whereinsaid producing comprises iteratively repeating said simulating, saidevaluating and said modifying, automatically by computer.
 22. A systemfor planning an ablation plan of a target tissue in a patient, thesystem comprising a processor configured to: simulate, one or moreoperations to lesion the target tissue, based on data characterizingpatient-specific anatomy comprising at least the target tissue, tocreate simulated results; evaluate, one or more criteria on saidsimulated results, said one or more criteria including a criterion toblock abnormal cardiac tissue conduction; and produce an ablation plancomprising a set of ablations applied along an extent of the targettissue; wherein the data include data on dielectric propertiesassociated with the target tissue; and wherein the ablation plan isproduced based on results of said evaluating.
 23. The system of claim22, wherein the data include data on thermal properties associated withthe target tissue.
 24. The system of claim 22, wherein the datacharacterize geometry of the target tissue, and the ablation plandescribes the adjustment of parameters of the ablations as a function ofgeometry along a planned target form of the lesion.
 25. The system ofclaim 22, wherein the simulated results comprise thermal simulation ofthe effect of lesioning on the patient-specific anatomy, based onthermal characteristics associated with the patient-specific anatomy.26. The system of claim 22, wherein the processor is configured toadjust one or both of the extent of the set of ablations and ablationparameters along the set of ablations, to avoid lesioning of thenon-target tissue.